PXR40RM Datasheet, PDF (131/1434 Pages) Freescale Semiconductor, Inc – PXR40 Microcontroller

Resets
4.7.2 Reset Configuration Timing
The timing diagram in Figure 4-4 shows the relationship between reset signals and the configuration pins
for a power-on reset. The timing diagram is valid for internal and external resets assuming that VDD and
VDD33 are within valid operating ranges. The WKPCFG and PLLCFG signals are applied at the assertion
of the internal reset signal (assertion of RSTOUT). The values of the configuration pins are latched 4 clock
cycles before the negation of the RSTOUT pin and stored in the Reset Status Register and SYNSR register.
VDD
POR
RESET
Internal
Reset
RSTOUT
Pins start to
drive/sample when
POR negates
2400¹ clocks
(4 clock cycles)
PLL
Crystal powering up or acquiring lock
PLL Locked
User drives
config pins relative
to RSTOUT
xTAL Clock Ready
PLLREF is
‘Don’t Care’ and WKPCFG is
treated as ‘1’ during POR assertion.
PLLREF and WKPCFG
are applied, but not latched.
WKPCFG,
BOOTCFG are
latched.
Note: 1. The clock count is dependent on the configuration of the PLL (refer to Section 4.3.2, RSTOUT). If the
PLL is configured in bypass mode, this clock count is 16000.
Figure 4-4. Reset Configuration Timing
4.7.3 Reset Weak Pull Up/Down Configuration
The signal on the WKPCFG pin determines whether specified eTPU and eMIOS pins are connected to
weak pull up or weak pull down devices at reset (see the Signal Description chapter for the eTPU and
eMIOS pins that are affected by WKPCFG). For all reset sources except the Software External Reset, the
WKPCFG pin is applied at the assertion of the internal reset signal (assertion of RSTOUT). If the
WKPCFG signal is logic high at this time, pull up devices will be enabled on the eTPU and eMIOS pins.
If the WKPCFG signal is logic low at the assertion of the internal reset signal, pull down devices will be
enabled on those pins. The value on WKPCFG must be held constant during reset to avoid oscillations on
Freescale Semiconductor
PXR40 Microcontroller Reference Manual, Rev. 1
4-11